1. Anti-Icing and De-Icing Compositions
Various de-icers (ice melters) have been studied for many years. Nonetheless, the compositions developed to date suffer from various disadvantages. The predominant de-icer remains sodium chloride, with its well known highly corrosive and environmentally deleterious properties. Approximately ten million tons of sodium chloride are used annually on roadways in the United States for de-icing purposes. Other more or less common de-icers either contain chlorides or phosphates and therefore are not environmentally safe and not acceptable by many local ordinances, or corrosive to steel and/or aluminum, or contain health-threatening compounds such as ethylene glycol, or are too inefficient, or too expensive (e.g., acetates, which cost about 20 to 30 times more than de-icers based on sodium chloride, and therefore are not practical for large-scale applications).
A desirable de-icing agent, liquid or solid, should possess a high ice-melting and ice-penetration capability (not less than that of sodium chloride or, better, calcium chloride), be a potent freezing point depressant (particularly when applied at subzero temperatures; it should be noted in this regard that sodium chloride is not a potent freezing point depressant, and can perform well at temperatures down to only about -6.degree. C., or +21.degree. F.), be readily biodegradable (if based on organic matter) and cause no damage to soil and its microflora, be physiologically acceptable to humans, animals, and fresh water basin inhabitants, produce no offensive smell and fire danger, be non-corrosive on metals (primarily, on iron and aluminum alloys, or whatever metals the de-icer practically comes into contact with; being non-corrosive in this context means does not cause weight loss of tested materials within experimental error, if widely accepted experimental protocols are followed, and/or does not cause rust formation on surface of tested steel coupons and in their test solutions, or blackening of aluminum or its alloys test coupons), and/or serve as an inhibitor of corrosion caused by water or other chemical agents. Furthermore, the de-icing agent should be affordable for the targeted applications (streets and roads, steel bridges, private driveways, walkways, railroad station platforms, concrete structures, runways, aircrafts, and the like). Hence, there is a wide selection of suggested de-icers and their compositions in the prior art.
Sodium acetate or potassium acetate (also calcium acetate and magnesium acetate) have been suggested in many studies as principal components of ice-melting compositions. U.S. Pat. Nos. 5,064,551 and 5,238,592 describe compositions comprising about 98% or more of acetates among all dissolved chemicals, concentration of acetates in water solution being from 15 to 70%, and preferably 25 to 60% by weight (U.S. Pat. No. 5,238,592), from 45% to 60%, and preferably at 50-53% (U.S. Pat. No. 5,064,551, European Patent Application No. 0375214), from 0.5% to 16% (U.S. Pat. No. 4,388,203), from 12% to 75% (U.S. Pat. No. 4,728,393), or from 40% to 60% (U.S. Pat. No. 5,350,533) by weight. U.S. Pat. No. 5,376,293 describes as a de-icer the crystalline double salt comprising from 25 to 75% w/w of sodium acetate and from 75 to 25%, respectively, of sodium formate. U.S. Pat. No. 5,104,562 describes a coolant composition, comprising of a mixture of potassium acetate and potassium formate as 40 to 60% w/w total concentrations in water (with potassium acetate from 1 to 9 parts by weight, and potassium formate from 1 to 2 parts in from 5 to 23 parts total by weight, including water).
U.S. Pat. No. 4,377,488 discloses a calcium acetate-based de-icing agent. U.S. Pat. Nos. 5,324,442 and 5,498,362 describe road de-icers comprising acetate salts of calcium and magnesium, and mixed calcium magnesium acetate (CMA, 25-40% by weight) and calcium magnesium propionate (50-75% by weight). The compositions were produced by treating water plant primary sedimentation basin residues (containing calcium and magnesium compounds) with acetic acid or a mixture of acetic and propionic acids, obtained either by fermentation (U.S. Pat. No. 5,324,442) or by other means (U.S. Pat. No. 5,498,362). CMA-based de-icers were also described in U.S. Pat. No. 4,636,467, which discloses a process for production of mixed calcium-magnesium acetate by anaerobic fermentation, and in U.S. Pat. No. 5,132,035.
U.S. Pat. No. 4,664,832 discloses a de-icer composition manufactured by reacting sodium carbonate with sawdust or other cellulosic biomass at high temperature and pressure, and containing, as a result of autohydrolysis and the subsequent chemical treatment, sodium salts of acetic, formic, and glycolic acids. U.S. Pat. No. 4,728,393 describes a de-icing product manufactured using black liquor obtained from a pulp mill operation, and comprising acetate salts, carbonate salts, formate salts, and pseudolactate salts.
Typically, disclosed de-icing formulations contain added buffer substances and/or corrosion inhibitors such as imidazole and/or triazole derivatives (e.g., U.S. Pat. Nos. 4,202,796, 4,382,008, 4,588,513, 4,592,853, 5,104,562, 5,238,592, 5,366,651), phosphates (e.g., U.S. Pat. Nos. 5,064,551, 5,238,592, 5,350,533, European Patent Application No. 0375214), soluble silicates (U.S. Pat. No. 5,350,533), nitrites (U.S. Pat. No. 5,064,551, European Patent Application No. 0375214), or other additives such as urea (U.S. Pat. No. 5,104,562), EDTA (U.S. Pat. Nos. 5,064,551, 5,132,035), sodium or potassium formate (U.S. Pat. Nos. 4,728,393, 5,064,551, 4,728,393, European Patent Application No. 0375214), glycols (U.S. Pat. No. 4,388,203), chlorides (U.S. Pat. No. 4,388,203), carbonates, pseudolactates from black liquor (U.S. Pat. No. 4,728,393), or unspecified amount of glycolic acid and/or lactic acid salts (U.S. Pat. No. 5,376,293). Some of these de-icer components are viewed by many as inefficient or environmentally damaging. Urea, for example, is ineffective as a de-icing agent at temperatures below -8 to -10.degree. C., is not a potent freezing point depressant, is corrosive, does promote the growth of weeds and algae in water basins, and readily decomposes into ammonia which is toxic to fish even in low concentration (see U.S. Pat. No. 5,064,551). The autohydrolysis composition, disclosed in U.S. Pat. No. 4,664,832 (mentioned above), has limited ice-penetration capability, significantly below that for sodium chloride under similar test conditions (see U.S. Pat. No. 5,376,293). Similarly, sodium formate is not as effective as sodium chloride as a de-icer, and is corrosive (see U.S. Pat. No. 5,376,293). Glycols are often resistant to biodegradation and hence present problems of pollution and contamination of water basins. Calcium magnesium acetate (CMA) is very dusty when dry, and spontaneously generates free acetic acid, even at pH levels as high as 9 (see U.S. Pat. No. 5,376,293). Moreover, the cost of CMA, which is produced by reacting dolomite with acetic acid (e.g., U.S. Pat. Nos. 4,636,467 and 4,855,071), is about twenty times or more than that of sodium chloride (see U.S. Pat. No. 5,324,442). Phosphates and nitrites have been barred by local ordinances in some areas because they are not environmentally safe (see U.S. Pat. No. 5,645,755). Nitrates as de-icers or their ingredients also are not desirable from an enviromental viewpoint (dangerous for sewage, and cause explosion hazard when dried, particularly in the presence of organic compounds). Ammonium salts as de-icers, similarly, cannot meet common environmental requirements concerning NH.sub.4.sup.+ content in non-aggressive waters (should be less than 15 mg per liter H.sub.2 O, see U.S. Pat. No. 4,448,702). De-icing agents are applied on traffic surfaces to be treated in an amount, in general, ranging from 10 to 100 g/m.sup.2 of ice- and/or snow-covered surface, depending on the outside temperature and the amount of ice and/or snow present (see, e.g., U.S. Pat. No. 5,238,592).
Salts of dibasic acids, such as an industrially obtained blend of adipic acid (30-35% w/w), glutaric acid (40-50% w/w), and succinic acid (20-25% w/w) have been recommended as an antifreeze solution in U.S. Pat. No. 4,448,702. These mixtures have been reported to provide very good corrosion prevention on metallic materials, such as cast iron, at pH levels of 7.5-7.8. However, while such compositions may be suitable for use in connection with heat/cold exchangers (coolers, radiators, as antifreeze compositions for internal combustion engines at temperatures ranging from -20.degree. C. to +100.degree. C.), anti-freeze and coolant compositions have different areas of practical application as compared with de-icers. Normally, antifreezes and coolants are not spread over land, streets, walkways, etc.; hence, requirements as to use, compositions, concentrations, viscosity, pH, types of corrosion inhibitors, etc. are different from those required for de-icers. Modes of characterization, test protocols, targeted functional parameters for antifreezes/coolants, on the one hand, and for ice-melting agents, on the other, are also different. Typically, the prior art in the area of antifreeze and coolant compositions does not provide any information on the ice-melting capacity of those compositions (e.g., dicarboxylic acid-based anti-freezes). The same is true with respect to the prior art in the area of aircraft de-icers and anti-icers.
Inorganic chlorides (such as sodium chloride, calcium chloride, magnesium chloride, potassium chloride, and combination thereof), in spite of their recognized potential for damage to the environment, continue to be offered as principal components of ice-melting agents. U.S. Pat. No. 5,645,755, for example, describes a composition comprising 80% sodium chloride, 18% magnesium chloride, and 2% calcium chloride by weight, combined with other additives and/or corrosion inhibitors such as 2-butyne-1,4-diol, urea, ammonium sulfate, fumaric acid, alkyl amine, oximine, or others. U.S. Pat. No. 5,531,931 discloses a sodium chloride-based composition, containing up to 25% w/w of magnesium chloride or calcium chloride, in combination with corrosion inhibitors such as either lanthanum salt, or salts of gluconic, ascorbic, tartaric, or saccharic acid. Gluconate and/or sorbitol are disclosed as corrosion inhibitors in sodium chloride brine solutions in U.S. Pat. No.5,330,683. U.S. Pat. No.4,654,157 discloses an ice-melting agent comprising a mixture of calcium chloride, magnesium chloride, and magnesium sulfate in various combinations. U.S. Pat. Nos. 4,803,007, 4,978,500, 5,296,167 describe sodium chloride- and calcium chloride-based compositions containing a mixture of phosphates as corrosion inhibitors. U.S. Pat. No. 4,512,907 describes an ice melter comprising sodium and/or potassium chloride mixed with urea and dried. U.S. Pat. No. 5,302,307 discloses a liquid de-icing composition comprising magnesium chloride and organic corrosion inhibitors such as triethanolamine, citric acid, and mixtures thereof. De-icing compositions comprising magnesium chloride and a polyphosphate salt or orthophosphate as corrosion inhibitors are disclosed in U.S. Pat. Nos. 4,990,278 and 5,211,868, respectively. U.S. Pat. No. 5,376,292 describes a de-icing composition comprising sodium chloride and water-soluble ferrocyanide or ferricyanide salt. U.S. Pat. No. 5,135,674 discloses a sodium chloride de-icer composition including between about 0.5% and 5% w/w of hydroxyethyl cellulose to minimize spalling of concrete to which the de-icing composition is applied. U.S. Pat. No. 4,824,588 describes a de-icing composition comprising sodium chloride, magnesium chloride, calcium chloride, or mixtures thereof, and saccharinic acid and lignosulfonate, the ratio of chloride and lignosulfonate being from about 16:1 to 1:2.25. Similarly, U.S. Pat. No. 4,668,416 describes a de-icing agent comprising sodium chloride, magnesium chloride, and/or calcium chloride and spent sulfite liquor, so that the ratio of chloride to lignosulfonate solids ranges from about 25:1 to 1:15. U.S. Pat. No. 4,986,925 discloses a de-icing agent comprising sodium chloride, lignosulfonate, and corrosion inhibitors. U.S. Pat. No. 4,676,918 discloses an ice-melting agent comprising a waste concentrate of alcohol distilling industry, 20 to 90% w/w of dry substance in water.
The prior art also discloses a number of solid de-icers applied onto a solid carrier, comprising, as a rule, sodium chloride and calcium chloride compositions. U.S. Pat. No. 4,849,171 describes such compositions in granular form, coated with superphosphate as a corrosion inhibitor, and magnesium oxide. U.S. Pat. No. 4,606,835 discloses a solid composition comprising chlorides, alcohols, bentonite and sodium metasilicate. Sodium chloride- and calcium chloride-based de-icers, pan agglomerated to form solid composition, are disclosed in U.S. Pat. No. 5,211,869. U.S. Pat. No. 4,377,488 describes a de-icing agent prepared by adding coarse limestone to calcium acetate solution in amounts up to 10% by weight and converting the solution into solid flakes. U.S. Pat. Nos. 5,599,475, 5,651,915, and 5,683,619 disclose calcium chloride-coated compositions used as solid de-icers (sodium chloride, potassium chloride, and urea), mixed with abrasives (sand, gravel) and absorbents (bentonite).
The prior art also describes other, less common road de-icers, such as inorganic nitrates (magnesium, calcium, ammonium, e.g., U.S. Pat. No. 4,108,669), inorganic phosphates (sodium, potassium, ammonium), ammonium sulfate, and low-molecular organic de-icers such as alcohols, glycols (e.g., U.S. Pat. Nos. 4,283,297, 4,597,884, 4,606,835), glycerin, urea (e.g., U.S. Pat. Nos. 4,283,297, 4,448,702, 4,597,884). German Patent No. 1459639 describes blends of formamide or its derivatives, low-molecular alcohols and glycolic ether for providing quick ice melting on solid surfaces. However, according to current knowledge formamide should not be used any longer in ice-melting compositions on account of its damaging effect to health (see U.S. Pat. No. 4,448,702). Czechoslovak Patent No. 184 118 describes mixtures based on ethanol and urea as ice-melters for airfields and streets, U.S. Pat. No. 3,624,243 recommends mixes of urea and ammonium nitrate with ethylene glycols as a de-icing liquid, and U.S. Pat. No. 2,980,620 describes ice-melting blends of ammonium sulfate, urea, and sodium nitrate with some corrosion inhibitors. The negative impact of these primary ingredients has been outlined above.
2. Pulp and Paper Sludge
Pulp and paper sludge (a byproduct of primary pulping operations, papermaking operations, recycle streams or waste paper pulping and the like) represents an environmental and disposal problem for manufacturers of pulp and paper. Generally, pulp and paper sludge is unsuitable for paper making, although it generally contains the same components--cellulose, lignin, hemicellulose, calcium carbonate, clay, and other inorganic components--as those present in the paper pulp itself. Paper sludge has traditionally been disposed of by landfilling, composting, incorporation into cement, and incineration. The latter option, in turn, creates another problem, namely, disposal of the resulting ash, a mixture of mineral components, which often constitutes up to 50% (and sometimes as much as 80% or higher) of the volume of the sludge itself.
The principal mineral components of pulp and paper sludge are calcium carbonate, in the form of precipitated calcium carbonate (PCC) or ground calcium carbonate (GCC), that typically constitutes 20% and up to 75% of dry sludge content, and clay. These two minerals are typically loaded into paper as a coating and filler to improve the mechanical characteristics as well as the appearance of paper. As a result, pulp and paper sludge, particularly mixed office paper sludge, consists of two major components, that is fiber and minerals, finely mixed with each other.
A typical recycling mill processes 600 tons of wastepaper per day, yielding 450 tons of pulp and producing 150 tons of pulp and paper sludge. Approximately 650 virgin and recycling mills currently under operation in North America, produce 9 million tons of pulp residue, 5 million tons of which is cellulose. 350 European pulp and paper mills, also virgin and recyclien, produce about 8 million tons of pulp residue, approximately 4 million tons of which is cellulose. The conversion of such waste material into value-added products has long been considered as a desirable goal.
One such application relevant to the present invention is granulation of pulp and paper sludge, as described in U.S. Pat. No. 5,730,371. GranTek Inc. (Green Bay, Wis.) manufactures controlled size dust-free granules, made of pulp and paper sludge, under the brand name BIODAC. The granules are a tight composite of organic and inorganic materials, that is cellulose fiber and minerals, and possess a developed porous structure. Another use of pulp and paper sludge, namely, a high-yield method for conversion of its cellulose component into glucose, is described in copending application Ser. No. 09/006,631, filed Jan. 13, 1998.